1. Field of the Invention
This invention relates generally to PGA (Pin Grid Array) product configuration using a laser trim process. More specifically, this invention relates to the calibration of the lasers used in the laser trim process. Even more specifically, this invention relates to a mechanical gauge and a method to use the mechanical gauge to determine the depth of the laser trim in both the metal and ceramic component of a substrate.
2. Discussion of the Related Art
A laser element is a metallized feature on the top surface of a PGA (Pin Grid Array). The laser element is formed as part of the substrate, using the same molybdenum metallization as other features on the substrate. It has nickel and gold plating. By design, it is part of the electrical circuit on the package and is necessary for proper operation of the product. When the laser element is intact, it connects two parts of a circuit. When cut (trimmed), the two parts of the circuit are not connected. This allows individual processors to be configured differently eliminating the need for the motherboard to be configured.
For example, the processor core operates at a clock rate that is a multiple of the system bus clock rate. BP is the number that represents the multiple of the clock rate. VID (Voltage ID) is a multi-bit setting that is used by a voltage regulator circuit on the motherboard to deliver correct voltage to the processor. The processor core operates at a clock rate that is a multiple of the system bus clock rate. Frequency ID (FID) is a number that represents that multiple of the clock rate, and is used by the xe2x80x9cNorthbridgexe2x80x9d component on the motherboard to send data to the processor at the correct rate. The processor functionality includes the ability to check for errors in system memory, when system memory with error correction is present. Access to this processor functionality can be disabled using this configuration option ECCEN_L (Error Correction Circuit Enable). L2SEL (L2 Select) is a multi-bit setting used by the processor to determine what size of L2 (level 2) cache memory is available. Even if a large L2 cache memory size is physically available on the silicon, access can be limited to a smaller size of cache memory using this configuration option. An RPAK (Resistor Pak) is a discrete component that contains an array of resistors. The resistors are required in certain of the processor configured (laser element) circuits, in order to allow proper electrical testing prior to configuration, and prior to shipping. Other parameters can be configured using laser elements.
Laser cut element and dimensional specification must be characterized and qualified on all substrates before the products are released to production. Each laser cut process has a set of requirements such as the following:
Frequency
Speed
Width of cut
Minimum Depth of cut
Maximum Depth of cut
Average Power
Shape of Cut
Because of the small dimensions, it is mandatory that the laser trim system complies with the set of requirements. Some of the above requirements set forth above are easily determined and controllable, such as frequency, speed, width of cut, average power, and shape of cut. However, arguably the most important dimension is the depth of cut. There is no current method to accurately determine the depth of cut currently being provided by a laser trim system. The two methods currently used to measure the depth of cut is a destructive cross sectioning and a gross functional microscopic measurement with low accuracy.
Therefore, what is needed is a simple method and system to accurately determine the depth of cut that the laser trim system will provide.
According to the present invention, the foregoing and other objects and advantages are obtained by a method of using a mechanical gauge to calibrate the laser utilized in a laser element cutting system.
In accordance with a first aspect of the invention, a mechanical gauge having metal pads disposed at the intersections of rows and columns on a surface of a substrate material is formed. The metal pads in each row vary in height and the metal pads in each column have the same height. The thickness of the substrate material underlying each pad varies form a single thickness to a thickness of two or more layers of substrate.
In accordance with a second aspect of the invention, the metal pads are formed in control pairs in columns from an odd numbered row and the next even numbered row.
In accordance with another aspect of the invention, the metal pad of each pair in the odd numbered row is formed on a single layer of substrate material and the metal pad of each pair in the even numbered row is formed from two or more layers of substrate material.
In accordance with another aspect of the invention, the metal pads on the mechanical gauge are subjected to a laser cut process and light is directed towards the mechanical gauge. The transmittal of light at the metal pad positions indicates that the metal pads and underlying layer or layers of substrate material have been cut.
In accordance with another aspect of the invention, the number of layers of substrate material in addition to the metal pad indicates the depth of the laser cut.
The described invention thus provides a method of utilizing a mechanical gauge to accurately determine the depth of a laser utilized in a laser element cutting process.
The present invention is better understood upon consideration of the detailed description below, in conjunction with the accompanying drawings. As will become readily apparent to those skilled in the art from the following description, there is shown and described an embodiment of this invention simply by way of illustration of the best mode to carry out the invention. As will be realized, the invention is capable of other embodiments and its several details are capable of modifications in various obvious aspects, all without departing from the scope of the invention. Accordingly, the drawings and detailed description will be regarded as illustrative in nature and not as restrictive.